Changes of phenolic acids and antioxidant activities during potherb mustard (Brassica juncea, Coss.) pickling

Phenolic acids in potherb mustard (Brassica juncea, Coss.) were determined and the effects of pickling methods on the contents of total free phenolic acids, total phenolic acids, total phenolics, and antioxidant activities were investigated. Gallic acid, protocatechuic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, p-coumaric acid, ferulic acid, and sinapic acid were identified in the present study. The contents of total free phenolic acids, total phenolic acids and total phenolics in fresh potherb mustard were 84.8 ± 0.58 μg/g dry weight (DW), 539 ± 1.36 μg/g DW, and 7.95 ± 0.28 mg/g DW, respectively. The total free phenolic acids increased during the pickling processes, but the total phenolic acids, total phenolics, and antioxidant activities decreased. However, after 5 weeks of fermentation, all the pickling methods retained over 70% of total phenolic contents and above 65% of antioxidant capacities. The results indicated that pickling processes were relatively good methods for the preservation of phenolic acids and antioxidants for potherb mustard.     

Antioxidant capacity,total phenolics,glucosinolates and colour parameters of rapeseed cultivars

The antioxidant capacity of twenty nine rapeseed varieties was determined by using ferric reducing antioxidant power (FRAP) and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) methods. Mean FRAP (3190–6326 μmol Trolox/100 g) and DPPH (3194–6346 μmol Trolox/100 g) values for methanolic extracts of rapeseed cultivars did not differ significantly. Moreover, the total content of phenolics (756–1324 mg sinapic acid/100 g), glucosinolates (4.2–87.5 μmol/g, respectively), erucic acid (0.0–56.1%) and colour parameters of the studied rapeseed cultivars were analysed. Antioxidant capacity determined by FRAP and DPPH methods correlated significantly with total phenolic content (TPC) in rapeseed cultivars (r = 0.9332, 0.9339, p < 0.001). Also, significant, inverse correlations were found between antioxidant capacity, total phenolics and luminosity (L^∗) or red colour intensity (a^∗) of rapeseed cultivars. Principal component analysis (PCA) allowed the rapeseed varieties to be differentiated based on their antioxidant capacities, total amounts of phenolics, glucosinolates, erucic acid and colour parameters.     

Genotypic effects on the phytochemical quality of seeds and sprouts from commercial broccoli cultivars

Determining ontogenic diversity in vegetables, in general or Brassicas in particular, regarding the bioactive content, is an interesting task since the most promising Brassicaceae foods could have the highest nutritional and health-promoting properties. Therefore, vitamin C, phenolic compounds, glucosinolate content, and total antioxidant capacity were evaluated in commercial cultivars of broccoli (Brassica oleracea var. italica; cv. Nubia, cv. Marathon and cv. Viola) seeds and during the sprouting period. Vitamin C was not detected in dormant seeds and its content increased with the germination, reaching values ranging from 53 (cv. Nubia) to 64 (cv. Marathon) mg/100 g FW, at the end of the monitored period (14days). The total glucosinolate content in seeds and 3-day-old sprouts was higher in cv. Marathon (1005 and 556 mg/100 g FW, respectively), however cv. Viola sprouts registered the highest glucosinolate content 7 and 14 days after sowing (235 and 208 mg/100 g FW, respectively). Aliphatic glucosinolates were more affected by genetic factors than the indolic glucosinolates, being glucoraphanin the predominant glucosinolate in cv. Nubia and cv. Marathon, whereas glucoiberin was the major glucosinolate in cv. Viola. The flavonoid and total phenolic content was significantly higher in cv. Viola. Also, seeds of this cultivar showed the highest antioxidant capacity (2.7 mg Trolox/g FW).     

Biosynthesis of phenolic antioxidants in carrot tissue increases with wounding intensity

Biosynthesis of phenolic antioxidants in three carrots cultivars (Navajo, Legend and Choctaw) were studied under different wounding intensities (A/W) during storage. Generated A/W of 4.2, 6.0 and 23.5 cm²/g, corresponded to slices, pies, and shreds, respectively. Soluble phenolics, antioxidant capacity (AOX), and PAL activity increased with A/W for all cultivars. Intense wounding (23.5 cm²/g) induced an ∼2.5- and ∼12.4-fold increase in soluble phenolics and AOX, respectively, after 4 days compared to whole carrots. Wounding induced the synthesis of mainly chlorogenic acid (5-CQA) and 3,5-dicaffeoylquinic acid. A higher proportion of 5-CQA in the phenolic mixture was responsible for an increasing specific AOX (809 and 1619 μg Trolox/mg phenolics for whole carrots and shreds, respectively, for Choctaw cultivar). Wounded carrots can be promoted as an inexpensive rich source of phenolic antioxidants for the regular diet. By simply increasing wounding stress intensity it is possible to enhance the biosynthesis of phenolic antioxidants.     

Contribution of low‐molecular‐weight antioxidants to the antioxidant capacity of raw and processed lentil seeds

In this study four cultivars of lentil originating from Spain were examined: cv Paula, cv Agueda, cv Almar and cv Alcor. Since consumption of these seeds after heat treatment and as sprouts has been popularised, the impact of cooking (up to 30 min) and germination process (in dark, at 25°C, for up to 4 days) on peroxyl radical‐trapping capacity (PRTC) and Trolox‐equivalent antioxidant capacity (TEAC) of the processed seeds was addressed. Also, changes in the content of low‐molecular‐weight antioxidants (LMWA) and soluble proteins in the course of cooking and germination were studied. The analyzed LMWA were: total phenolics, tocopherols (α‐T, β‐T, γ‐T, δ‐T( reduced glutathione, and L ‐ascorbic acid. On the basis of the results obtained, the contribution of LMWA and soluble proteins to the PRTC and TEAC of raw, cooked, and germinated lentil seeds was calculated by multiple mean values for the content of investigated compounds and their relative potential with respect to Trolox. The results showed a very high molar percentage contribution of phenolic compounds and low contribution of tocopherols, glutathione, soluble proteins, and ascorbate (only in germinated seeds) to the total TEAC and total PRTC calculated as a sum of data provided for phosphate‐buffered and 80% methanolic extracts of raw and processed lentil seeds.     

Effect of preliminary processing and method of preservation on the content of selected antioxidative compounds in kale (Brassica oleracea L. var. acephala) leaves

Vitamin C and polyphenol content as well as total antioxidative activity were investigated in fresh leaves of kale; in leaves after blanching or cooking; and in frozen and canned leaves. In 100 g fresh matter, kale leaves contained 384.9 mg polyphenols and 112.1 mg vitamin C, with a Trolox equivalent antioxidant capacity (TEAC) level of 1175 μM Trolox. Of the polyphenols identified in kale leaves, ferulic acid occurred in the highest amount (240.44 mg/100 g, constituting 62% of total polyphenols). Freezing was a better method of preserving kale leaves since the loss of nutritive constituents was lower than in the case of canning. Depending on preliminary processing and storage temperature, after one-year storage frozen leaves contained 82.9–171.3 mg polyphenols and 39.3–65.4 mg vitamin C, with TEAC at the level of 501–681 μM Trolox in 100 g. In canned leaves these values were: 91.3–94.1 mg polyphenols, 16.1–19.3 mg vitamin C and 268–293 μM Trolox.     

Phenolics and antioxidant activity of lentil and pea hulls

Hulls obtained by pilot-scale dehulling process from green and red lentils and yellow peas were fractionated into hulls (> 500 ??m) and residues (< 500 ??m). These fractions together with the corresponding whole seeds were extracted with four solvents, aqueous (70%) acetone, (80%) ethanol, hot water (70-80 °C) and water (22 ± 1 °C) and evaluated for antioxidant activity in relation to phenolic contents. Aqueous acetone (70%, v/v) extracted the highest level of total phenolics at about 87 mg of catechin equivalent per gram of sample from lentil hulls followed by hot water, water and aqueous ethanol (80%, v/v). Red lentil hull with maximum concentration of phenolic compounds exhibited the strongest antioxidant activity of 260 mg (1040 ??M) trolox equivalent/g hull. Hot water and water extracted significantly higher total phenolics from whole pulse and their residue than other solvents, but with weaker antioxidant activity. Aqueous ethanol was always the best extractant of phenolic antioxidant from yellow pea irrespective of its millstream. The most potent phenolic antioxidant was obtained from water extract of green and red lentil hulls, followed by those extracted with ethanol, acetone, and hot water. Total phenolic content was highly correlated with antioxidant activity of pulses and its millstreams.     

Determination of total phenolic content and antioxidant capacity of onion (Allium cepa) and shallot (Allium oschaninii) using infrared spectroscopy

Total phenolic content (TPC) and total antioxidant capacity (TAC) of four onion varieties (red, white, yellow and sweet) and shallot from selected locations (Washington, Idaho, Oregon, Texas and Georgia) were determined using Fourier transform infrared (FT-IR) spectroscopy (4000–400 cm⁻¹). The Folin–Ciocalteu (F–C) assay was used to quantify TPC and three assays were used to determine TAC, including 2,2-diphenyl-picrylhydrazyl (DPPH) assay, Trolox equivalent antioxidant capacity (TEAC) assay and ferric reducing antioxidant power (FRAP) assay. Partial least squares regression (PLSR) with cross-validation (leave-one-out) was conducted on onion and shallot extracts (n = 200) and their corresponding F–C, DPPH, TEAC and FRAP values were employed to obtain four independent calibration models for predicting TPC and TAC for the extracts. Spectra from an extra 19 independent extracts were used as an external validation set for prediction. A correlation of r > 0.95 was obtained between FT-IR predicted and reference values (by F–C, DPPH, TEAC and FRAP assay) with standard errors of calibration (SEC) and standard errors of cross-validation (SECV) less than 2.85, 0.35 and 0.45 μmol Trolox/g FW of extracts for TEAC, FRAP and DPPH assay, respectively; and 0.36 mg gallic acid/g FW of extracts for the F–C assay. In addition, cluster analysis (principal component analysis (PCA)) and discriminant function analysis (DFA) could differentiate varieties of onions and shallot based upon infrared spectral features. Loading plots for the various chemometrics models indicated that hydroxyl and phenolic functional groups were most closely correlated with antioxidant capacity. The use of mid-infrared spectroscopy to predict the total antioxidant capacity of vegetables provides a rapid and precise alternative to traditional wet chemistry analysis.     

Phenolic content and antioxidant capacity of tropical highland blackberry (Rubus adenotrichus Schltdl.) during three edible maturity stages

Tropical highland blackberry (Rubus adenotrichus Schltdl.) is a good source of antioxidants and contains appreciable levels of phenolic compounds, mainly ellagitannins and anthocyanins. This study examined the influence of three ripening stages on phenolic contents. Major anthocyanin pigments increased from 0.20 (red fruit) to 1.34 mg g⁻¹ fresh weight (FW) (fully ripe fruit), whereas ellagitannins and ellagic acid derivatives dropped from 3.8 to 2.2 mg ellagic acid equivalents g⁻¹ (FW). Flavonols also dropped from 5.1 to 2.0 mg quercetin equivalents 100 g⁻¹ (FW). Consequently, values for total phenolic compounds ranged from 5.8 to 5.2 mg gallic acid equivalents g⁻¹ (FW), showing no specific trend. Antioxidant activity (H-ORAC) increased from 38.29 to 64.00 μmol of Trolox equivalents g⁻¹ (FW) during ripening. When compared with other commercial cultivars, R. adenotrichus stands out for high H-ORAC value, although comparatively it possesses low anthocyanin content and average total phenolic content.     

Microbial profiles of on-line--procured sprouting seeds and potential hazards associated with enterotoxigenic Bacillus spp. in homegrown sprouts

We examined the microbiological quality of sprouting seeds sold through the Internet. Overall, five types of seeds each from six organic and six conventional sources were evaluated. The growth and toxin production of naturally occurring Bacillus spp. in sprouts produced using home-scale sprouting devices also were investigated. For alfalfa, broccoli, lentil, mungbean, and radish seeds, the average microbial counts were 3.3, 4.0, 2.8, 3.5, and 3.6 log CFU/g, presumptive B. cereus counts were 0.7, 1.0, 0.8, 1.0, and 0.9 log CFU/g, and total coliform counts were -0.3, -0.4, -0.5, 0.0, and -0.4 log of the most probable number per gram, respectively. No Salmonella, Escherichia coli O157, other fecal coliforms, or Staphylococcus aureus was found on seeds. Compared with conventional seeds, the organic seeds had lower or equivalent counts for total microorganisms, presumptive B. cereus, and total coliforms. When seeds were sprouting using a glass jar, the growth of presumptive B. cereus was significant for radish and broccoli but not for alfalfa, lentil, and mungbean sprouts; the counts exceeded 5.0 log CFU/g in radish sprouts. When sprouts were grown using an automatic sprouting device, presumptive B. cereus showed slight growth (< 3.0 log cycles) in radish, broccoli, and mungbean sprouts but no growth in alfalfa and lentil sprouts. Although the presumptive B. cereus isolates were enterotoxigenic, they did not produce or accumulate detectable levels of diarrheal toxins in freshly produced sprouts.     

Effect of 1-MCP treatment on postharvest quality characters, antioxidants and glucosinolates of Chinese kale

The effect of 1-methylcyclopropene (1-MCP) on postharvest characters, antioxidants and glucosinolate contents in bolting stems of Chinese kale (Brassica alboglabra Bailey) was investigated. Chinese kale was treated with air (control) and 10 μl l⁻¹ of 1-MCP for 24 h, followed by storage for up to seven days at 20 °C. 1-MCP treatment obviously extended the shelf life, delayed weight loss and decreased the rate of softening, chlorophyll degradation and changes in hue angle. In addition, ethylene production was suppressed and the respiration rate declined. Moreover, 1-MCP treatment postponed the decrease of ascorbic acid, carotenoids and glucosinolates. 1-MCP treatment of bolting stems also delayed the accumulation of total phenolics, and maintained a high level of antioxidant capacity. These results demonstrate that 1-MCP treatment is a good practice for extending shelf life, maintaining the appearance and nutrient value, and reducing the loss of health-promoting compounds, particularly antioxidants and glucosinolates in the Chinese kale.     

Concentration of camu–camu juice by the coupling of reverse osmosis and osmotic evaporation processes

The objective of this work was to evaluate the technical feasibility of coupling two membrane separation processes, reverse osmosis (RO) and osmotic evaporation (OE), in order to concentrate clarified camu–camu juice, focusing on the vitamin C, phenolic compounds and antioxidant activity of the final product. The juice was firstly pre-concentrated by RO, reaching 285 g kg⁻¹ of soluble solids. During this step, the juice’s osmotic pressure showed to be the main factor controlling mass transfer. The juice was then concentrated by OE, reaching 530 g kg⁻¹ of soluble solids. Vitamin C, total phenolics and antioxidant activity levels of 94.6 g ascorbic acid kg⁻¹, 105.2 g galic acid kg⁻¹ and 762 mmol Trolox kg⁻¹, respectively, were achieved in the final product. The use of integrated membrane processes proved to be an interesting alternative to the concentration of thermosensitive juices, reaching concentration levels up to 7 times for camu–camu juice’s bioactive compounds.     

Contribution of low-molecular-weight antioxidants to the antioxidant capacity of raw and processed lentil seeds

In this study four cultivars of lentil originating from Spain were examined: cv Paula, cv Agueda, cv Almar and cv Alcor. Since consumption of these seeds after heat treatment and as sprouts has been popularised, the impact of cooking (up to 30 min) and germination process (in dark, at 25 degrees C, for up to 4 days) on peroxyl radical-trapping capacity (PRTC) and Trolox-equivalent antioxidant capacity (TEAC) of the processed seeds was addressed. Also, changes in the content of low-molecular-weight antioxidants (LMWA) and soluble proteins in the course of cooking and germination were studied. The analyzed LMWAwere: total phenolics, tocopherols (alpha-T, beta-T, gamma-T, delta-T), reduced glutathione, and L-ascorbic acid. On the basis of the results obtained, the contribution of LMWA and soluble proteins to the PRTC and TEAC of raw, cooked, and germinated lentil seeds was calculated by multiple mean values for the content of investigated compounds and their relative potential with respect to Trolox. The results showed avery high molar percentage contribution of phenolic compounds and low contribution of tocopherols, glutathione, soluble proteins, and ascorbate (only in germinated seeds) to the total TEAC and total PRTC calculated as a sum of data provided for phosphate-buffered and 80% methanolic extracts of raw and processed lentil seeds.     

Effect of baking on dietary fibre and phenolics of muffins incorporated with apple skin powder

Apple fruit skin, a rich source of dietary fibre and phenolics, is a by-product of apple processing. The effect of baking on the dietary fibre, phenolics, and total antioxidant capacity was investigated using a model system of muffins incorporated with dried apple skin powder (ASP) as a value-added food ingredient. The blanched, dehydrated, and ground ASP contained approximately 41% total dietary fibre and oxygen radical absorption capacity (ORAC) of 52 mg Trolox equivalents g⁻¹ dry weight. The total dietary fibre content, total phenolic content, and total antioxidant capacity of muffins were positively correlated to the amount of ASP incorporated into muffins. The mean percent recovery of quercetin glycosides, catechins, chlorogenic acid, phloridzin, and cyanidin galactoside after baking were 61%, 57%, 53%, 44%, and 20%.     

Phenolic compound profile of selected vegetables frequently consumed by African Americans in the southeast United States

The phenolic composition of vegetables commonly consumed by African Americans in the southeast United States was analyzed with HPLC–MS. The vegetable samples included collard greens, mustard greens, kale, okra, sweet potato greens, green onion, butter beans, butter peas, purple hull peas, rutabagas, eggplant, and purslane. Five compounds out of total 29 peaks detected from the 12 samples – caffeic acid, ferulic acid, quercetin, kaempferol, and isorhamnetin – were identified. No gallic acid, p-coumaric acid, myricetin, luteolin, apigenin, hesperetin, naringenin, or flavanols was detected. The major flavonoids were isorhamnetin, quercetin and kaempferol. Isorhamnetin was found in kale, mustard greens, and purslane. The content ranged from 2.8 to 23.6 mg/100 g fresh edible part. Quercetin was found in collard greens, mustard greens, kale, okra, sweet potato greens, purple hull peas, and purslane. The content ranged from 1.3 to 31.8 mg/100 g with the highest content in kale and lowest content in purslane. Kaempferol was found in collard greens, mustard greens, kale, sweet potato greens, green onion, and purslane. The content ranged from 1.1 to 90.5 mg/100 g. Caffeic acid was only found in sweet potato greens. Ferulic acid was found in collard greens, mustard greens, kale, okra, purple hull peas, and purslane. Although some peaks were found in eggplant, butter beans, butter peas and rutabagas, these peaks were not identified due to lack of reference compound and no flavonoid or phenolic acid was quantified in these samples. The results suggest that these indigenous vegetables among African Americans are good sources of the phenolic compounds, which can be useful for the prevention of cardiovascular and other chronic diseases.     

Phenolic acid contents of kale (Brassica oleraceae L. var. acephala DC.) extracts and their antioxidant and antibacterial activities

Nine phenolic acids were identified and quantified by HPLC–MS in leaves and 10 in seeds of kale (black cabbage). The free, ester (methanol-soluble), glycoside and ester-bound (methanol-insoluble) phenolic acid contents of the leaves were 487, 532, 4989 and 6402 ng/g fresh weight, respectively. Ferulic and caffeic acids (total contents; 4269 and 4887 ng/g, respectively) were the most abundant. The seed contents of these fractions were 1993, 1477, 1231 and 4909 ng/g dry weight (DW), respectively, and sinapic acid was the most abundant (5037 ng/g DW). The fractions’ total phenolic contents, determined colorimetrically, were highly correlated with their DPPH scavenging capacity, and in antimicrobial activity assays, with nine test organisms representing a wide array of taxa, all of the fractions were effective against Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis and (most strongly) Moraxella catarrhalis. Antimicrobial and antioxidant activities of kale phenolics in free and conjugated forms are discussed.     

Phenolic content and antioxidant capacity of hybrid variety cocoa beans

Cocoa (Theobroma cacao L.) is a major, economically important, international crop and has been associated with several nutritional benefits including high antioxidant capacity. New cocoa hybrids have been developed in Ghana that exhibit resistance to pest damage during storage. The aim of this work was to assess the phenolic content and antioxidant capacity of these new hybrids in comparison to more traditional cocoa varieties. Total extractable phenolics were similar in all the four hybrids tested ranging from 69.9 to 81.6 FAE g⁻¹. These levels were very similar to that extracted from traditional beans (73.8 ± 2.5 FAE g⁻¹). The “phenolic profile” was determined by HPLC. A total of 25 peaks was observed but there were only minor differences in this profile between traditional and hybrid bean extracts. Antioxidant capacity was determined using the FRAP assay and traditional beans were found to possess 12.4 μmol TE g⁻¹. In comparison the hybrid beans had antioxidant capacities ranging from 21.6 to 45.5 μmol TE g⁻¹, and these were significantly higher than in the traditional beans for three out of the four hybrids. Since the phenolic and antioxidant levels and in these hybrid varieties were either similar to, or higher than, that obtained from traditional beans, the introduction of these new varieties would be unlikely to impact detrimentally on these nutritional components of the beans.     

Extraction of phenolics from Vitis vinifera wastes using non-conventional techniques

Polyphenols, the well known naturally occurring antioxidants, are the most abundant secondary metabolites in grape wastes. Herein we investigate several non-conventional extraction methods vs classic solid–liquid extraction (SLE) to obtain phenolic compounds from grape seeds and skins. We compared SLE, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and high pressure and temperature extraction (HPTE) in term of extraction yield and antioxidant power of the extract. Solvent of choice between methanol and ethanol was the former, both for skins and seeds. Quali-quantitative analyses were performed using colorimetric and HPLC methods. The highest content in total polyphenols, o-diphenols and flavonoids, both for seeds (108.3, 47.0 mg_GAE g_DW⁻¹, 47.2 mg_CE g_DW⁻¹) and skins (34.2, 10.1 mg_GAE g_DW⁻¹, 21.6 mg_CE g_DW⁻¹) was obtained with HPTE working in a Parr reactor. While the highest antiradical power was determined in seeds extracts from MAE (78.6 μl_extract μg_DPPH⁻¹). Prolonged extraction times (over 30 min) further increased the amount of total polyphenols, while progressively decreased the amount of flavonoids and the antiradical power.